Expansion of eastern Mediterranean Middle Paleolithic into the desert region in early marine isotopic stage 5

Marine Isotopic Stage 5 is associated with wetter climatic conditions in the Saharo-Arabian deserts. This stage also corresponds to the establishment of Middle Paleolithic hominins and their associated material culture in two geographical provinces in southwest Asia—the Eastern Mediterranean woodland and the Arabian Peninsula desert. The lithic industry of the Eastern Mediterranean is characterized by the centripetal Levallois method, whereas the Nubian Levallois method characterizes the populations of the Arabian desert. The Negev Desert, situated between these regions is a key area to comprehend population movement in correlation to climatic zones. This investigation addresses the nature of the Middle Paleolithic settlement in the Negev Desert during MIS 5 by studying the site of Nahal Aqev. High resolution chronological results based on luminescence dating and cryptotephra show the site was occupied from MIS 5e to MIS 5d. The lithic industries at Nahal Aqev are dominated by centripetal Levallois core method. These data demonstrate that Nahal Aqev is much closer in its cultural attributes to the Eastern Mediterranean Middle Paleolithic than to the Arabian Desert entity. We conclude that Nahal Aqev represents an expansion of Middle Paleolithic groups from the Mediterranean woodland into the desert, triggered by better climatic conditions. These groups possibly interacted with hominin groups bearing the Nubian core tradition from the vast region of Arabia.


Fig. S1.1: Orthophoto and cross sections (A-A', B-B') of Nahal Aqev showing site location, terraces and travertines.
The second stage of incision is related to a widespread tectonic phase that uplifted, tilted and faulted the entire Negev toward the Arava Valley in the east, at ca. 1.5-1 Ma (3)(4). This eastward tilt caused a general shift of the drainage orientation in Nahal Zin and its tributaries, including Nahal Aqev, toward the Dead Sea basin (3). This process was accompanied by a deep incision of Nahal Aqev, forming its present level, ca. 100 m below its previous Early Pleistocene level.

Alluvial terraces in the lower Aqev canyon
The incision of the lower canyon was a gradual process that took place during the Pleistocene.
Nevertheless, during this time, two phases of deposition of fluvial and alluvial deposits occurred ( Fig. S1.1B). These depositions formed terraces labeled Q2 and Q3, following the definition of Quaternary morphostratigraphic units presented in Avni and Wieler (5) and Avni et al., (6)(7). The Q2 terrace system is associated with the gradual aggradation of alluvial deposits accumulating to an elevation of ca. 30-20 m above the present stream bed along the mainstream channel and its major tributaries. At present Q2 terraces are preserved in several patches in Nahal Aqev and associated with local travertines. The terraces are composed of a mixture of rock fragments, gravels and desert dust and are correlated with talus and colluvium deposits that accumulated simultaneously along the steep slopes of the lower canyon ( Fig. S1.2). The Q2 terrace system and its associated talus deposits are dated roughly to 200-100 ka (6)(7).
However, more research is needed for more precise dating of this phase of accumulation.
After the end of the depositional phase of the Q2 terrace, it was affected by an erosional phase corresponding with MIS 5 that incised some of the Q2 terraces down to the bedrock. This phase is associated with regional travertines that were deposited directly on the exposed bedrock or on top of preserved Q2 talus relicts. In some cases, local accumulation of colluvium deposits is recognized, similar to the colluvium on which the archaeological site is embedded (Fig. S1.2).
The termination of MIS 5 was subsequently followed by a new accumulation phase of alluvial deposits which accumulated within the lower Nahal Aqev canyon, up to 8-10 m above the present streambed. These sediments formed a prominent fluvial terrace, marked as the Q3 terrace, that is mostly composed of desert dust, known also as desert loess (8), interbedded with rock fragments of local origin. The Q3 terraces are linked to the nearby canyon slopes and cliffs by colluvium mantels. In several locations in the Negev Highlands these terraces were dated to ca. 80-18 ka BP (7,(9)(10).
Following the major Late Pleistocene-Holocene climate shift, dated to , Nahal Aqev began incising into the Q3 alluvial terraces to form its present stream bed that is slightly incised into the bedrock exposed below the base of the Q3 terrace.  2. A stream bed travertine, 15-20 cm thick, is located 50 m upstream of the archeological site at the contact between the chalk and flint beds of the Mor Formation and the alluvial deposit at the base of relict Q2 terraces ( Fig. S1.2). The travertine is composed of small gravels cemented by calcium carbonate, resulting from carbonate-saturated spring-water that flowed along this contact before the deposition of Q2 terrace. Similar accumulations are visible along the main streambed of Nahal Aqev above the lower Aqev spring. At the moment no direct date is available for this travertine and its relation to the archeological site is unclear.
3. Holocene travertines were noted attached to the current cliffs in the vicinity of the site, 250 m to the southwest, which are 80-100 m above channel bed. At this location, a currently dry waterfall formed. The lower part of the waterfall is partly covered by a porous travertine, 20-50 cm thick, vertically attached to the cliff. This travertine indicates that in the past, a spring emerged from fissures in the rocks exposed by the waterfall, contributing water to the lower part of the tributary that flowed at the foot of the archeological site. The association of the travertine to the present cliff hints to its relatively young, probably Holocene, age.
At present travertines are accumulating near active springs and on wet rock surfaces in the vicinity to the Ein Aqev lower spring, some 500 m to the north of the archeological site.

Section 2. The site of Nahal Aqev
Investigations of the Middle Paleolithic (MP) period were conducted in the Negev during the 1970's in the framework of the Central Negev Project directed by Marks (12)(13)(14). Fieldwork performed in various areas in the Negev highland revealed a density of MP sites in the Avdat-Aqev region. Among the discovered sites were two larger occupations interpreted as basecamps, Rosh Ein Mor (D-15) and Nahal Aqev (D-35) sites, and nine ephemeral occurrences (15)(16)(17)(18). Rosh Ein Mor and Nahal Aqev were the better-preserved stratified sites, each composed of several sedimentological units. The lithic industries of the two sites were assigned to the Early MP, as they were assumed to correspond to Tabun D-type of the Mediterranean woodland region (19). However, dating efforts of the two sites did not provide a clear assignment to the ascribed Early MP. At Rosh Ein Mor, uranium series dating of ostrich eggshells provided an age of ca. 200 ka, but thermoluminescence (TL) dating of burnt flints from the same contexts provided a range of 48-14 ka (20)(21). Most recent dating of calcite crusts coating lithic artifacts have assigned Rosh Ein Mor to the Late MP corresponding to MIS 4 (22). Nahal Aqev was not directly dated, and its ascribed age of ca. 80 ka was based on uranium series dating of travertine deposits located ca. 150 meters southwest of the site (11).
The Nahal Aqev site is located at an elevation of 430 m asl, 500 m upstream from Ein Aqev spring ( Fig. S2.1). Two excavation seasons were conducted at the site, in 1972 and 1974. In the first season two geological trenches were dug into the terrace deposits ( Fig. S2.2). Trench 1 transected the terrace perpendicular to its long axis, from the east to the west. Trench 2 was dug along the western slope of the terrace. In the second season an excavation area was opened on the western side of the terrace, at the contact between Trench 1 and Trench 2. The excavations revealed three archaeological levels bearing flint artifacts from the MP period. Level 3, up to 70 cm thick, was the best preserved and had the thickest accumulation of lithic artifacts.  In 2015-2016 we conducted two excavation seasons at Nahal Aqev (permits # G-27/15; G-88/16 from the Israel Antiquities Authority) (23). The fieldwork was initially carried out in the old excavation area of 1974 ( Fig. S2.3). The old excavation sections were cleaned, and a new area composed of 12 m² was opened to the south. In addition, a new geological trench (Trench 3, ca. 8 m long, 40 cm wide and 50 cm deep) was excavated from the new excavation area down to the base of the alluvial terrace along its western slope. In total, 18 sedimentological units representing one geomorphological sequence, were recognized (Fig. 2 manuscript). Units 1-7 occur in the excavation area and Units 8-18 in the geological trench. Excavation of archaeological layers was carried out in Units 3-7, 9 and 11 while the rest of the units were sectioned and cleaned but not excavated. Excavation was conducted in a 1X1 m grid in 10-5 cm spits. All sediments were dry sieved using 2 mm mesh.

Archaeological horizons
Three archaeological horizons displaying concentrations of horizontally embedded artifacts were recognized in the new excavation (Fig. 2D manuscript). The uppermost archaeological horizon (Level A), embedded in Unit 7, was exposed in the old excavation area, below what was previously defined by Munday (17) as Level 3. This 20 cm thick level is composed of flint artifacts embedded horizontally within fine-grained silty sediment (Fig. S2.5). The level was excavated in an area of ~ 7 m², mainly below the old excavation area, but also in the western slope of the terrace.
Unit 9 is a thin layer composed of grey clayish sediment embedded between two bedded gravel units. The archaeological horizon, Level B, embedded in this unit was only exposed in a small area of ~ 1 m² and therfore our understanding of its nature is limited.
The lowermost archaeological horizon, Level C, and hence the earliest occupation at the site, is embedded in Unit 11 which is a silty sand sediment (Fig. S2.6). This horizon is ca. 30 cm thick, it is rich and very well preserved and is composed of flint artifact laying horizontally, ostrich eggshell fragments and a hearth.

Section 3. Evidence for a hearth feature in Unit 11
We noted concentrations of flints in Unit 11, some of which were clearly fire-cracked and associated with dark local patches of sediments. FTIR analysis of the sediments in and around these dark patches showed that the dark patches contained substantial amounts of gypsum, calcite, clay and quartz, whereas the sediments around the patches contained only quartz, clay and calcite ( Fig. S3.1). This raised the interesting possibility that the gypsum in these patches could actually result from fires where Tamarix wood was one of the fuel components. It is known that the ash of the wood of the Tamarix is composed of the calcium sulfate mineral, anhydrite (25)(26) and the fresh wood contains crystals of calcium sulfate hemihydrate (basanite) (27). After burning these crystals presumably transform into anhydrite and anhydrite ash crystals would presumably undergo hydration over time to form gypsum, as was shown experimentally (28). Tamarix trees are abundant in the dry riverbed in the Nahal Aqev region today. We therefore carried out a series of experiments to examine this hypothesis. Sediments with gypsum are present outside the site derived from various geological horizons.
We examined the gypsum crystal morphologies in Unit 11 using a light microscope to determine whether their morphologies differed from those in the control sediments from outside the site.
We could not identify any unique morphologies. It has been noted that the crystals in freshly prepared Tamarix ash do have characteristic rhombohedral shapes (28), but rhombohedral shaped crystals were not observed in Unit 11 sediments. We presume that the crystal shape changed either during the transformation from anhydrite to gypsum, or over time since burial.
We then examined the clay in the FTIR spectra from 4 gypsum-rich sediments and 3 sediments around the gypsum-rich patches, all from Unit 11 (see Figure S3.1 for locations) (Fig. S3.2). The hydroxyl peaks of the clay spectrum located at 3691 and 3620cm -1 are very small or absent in the gypsum-rich samples but are small but prominent in the surrounding sediments. When clay is heated above around 500 °C (29) these hydroxyl peaks disappear. At higher temperatures the peak at 512cm -1 is diminished and the main peak at around 1032cm -1 shifts to higher wavenumbers. The clays in the gypsum-rich sediments do not show these features. We therefore conclude that the clays associated with the gypsum were exposed to temperatures around 500 °C. This is therefore consistent with these gypsum-rich patches containing Tamarix ash and were hence hearths. Note that the small hydroxyl peaks of the clay minerals at 3691 and 3620 cm -1 are prominent in the 3 spectra at the bottom of the figure that do not contain gypsum, but are absent or barely visible in the spectra that do contain gypsum. This indicates that the sediments containing gypsum have been exposed to temperatures around 500°C. The spectra were all normalized to the same heights of the main 1032cm -1 peak of clay. The manner in which the parameters for the grinding curve of gypsum (see below) were obtained are shown in the spectrum of sample 2892.

Parameter A is the heights of peaks (a) and (b) divided by the height of the lowest point between them (c). Parameter B is the height of peak (e) divided by the height of peak (d).
As calcite from wood ash is more disordered at the atomic level than geological calcite, we examined the possibility that the gypsum itself was more disordered at the atomic level even though it had diagenetically hydrated from anhydrite to gypsum. We therefore produced grinding curves for the pure gypsum control samples from outside the site by plotting parameter A against parameter B as defined in the legend of Figure S3.2. Figure S3.3 compares the grinding curves of the gypsum in the dark patches in Layer 11 to the gypsum-rich geological controls. All the gypsum-rich sediment samples from Unit 11 fall slightly above the 3 control curves derived from geological gypsum from this area. This may indicate that they are less well ordered.
However, the gypsum from two of the control sediments taken from the top of the terrace about 100 meters south of the site, also had the same degree of disorder. Thus, degree of atomic disorder is not unique to the gypsum in the dark patches from Unit 11. Note that we cannot determine the atomic disorder of freshly prepared Tamarix ash, as it is anhydrite and not gypsum. As noted, over time the anhydrite can be expected to hydrate and become gypsum (28).
Thus, the observations consistent with the gypsum in these patches originating from hearths in which Tamarix wood was burned are: 1. The presence of localized patches surrounded by sediment without gypsum, which is consistent with these patches being hearths. 2. The absence or reduction of the clay hydroxyl peaks indicating heating of the sediments in the patches. 3.
The association of the gypsum-rich samples with fire-cracked flint debitage, indicating that fires were made on the Unit 11 surface.
Patches of gypsum-rich sediments are also present in Unit 7. Unit 7 contains abundant flint debitage, some of which can be refitted. It is therefore clearly an occupation layer, and the dark gypsum-rich patches in Unit 7 may also be remnants of hearths.

Section 4. The lithic assemblages
The lithic assemblages from the renewed excavation comprise 17,804 artifacts. Of these 6,656 (37.4%) are larger than 2 cm (S4 Table 1 extremely fresh and well preserved, including those from sections and surface materials. For the samples subjected to attribute analysis (N=2861), 97% of items were fresh and 3% slightly abraded. High number (55%) of the sample items were broken, partially due to fire, mainly in Unit 11.
Most of the flint items (81% of analyzed sample) were made using brown and grey raw material, probably from the Early Eocene Mor Formation cropping out around the site (30). Few items (5%, and none of the cores) were made using semi-translucent brown flint, most likely from the Mishash Formation that can be found ~2 km to the north of the site (5) or collected from gravels found along the main channel of the Aqev stream. Other flint types are very rare or cannot be assigned to a specific geological source.
All in situ layers show a high percentage of artifacts smaller than 2 cm (chips, 62.6%). In the upper Units 7 and 9 the high proportion of small artifacts seems to be the outcome of knapping on site. In Unit 11 the high proportion of small artifacts clearly also results from burning and flint bursting/cracking by fire. respectively) while cores, core trimming elements (CTE) and blades occur in low frequencies.

S4
The dominant reduction sequence in all assemblages is centripetal Levallois in recurrent mode.
This tendency is seen on flakes and Levallois blank frequencies as well as on cores (S4 Table 1   Nevertheless, centripetal knapping strategy is the most prominent in the whole assemblage, as seen on items with identifiable scar pattern (Figs. S4. [4][5], both Levallois and non-Levallois, probably partly derived from the same reduction sequence. Cores constitute 2.9% of the flint items >2 cm in the assemblage, with a lower frequency (1.2%) in Unit 11. Levallois cores are the largest group within the core types in all assemblages except for Unit 9, where the small sample size may have affected the composition (Fig. S4.3). Centripetal cores are clearly the most common type of the Levallois cores in all units (Fig. S4.4).
The hierarchical surface cores in the assemblage are most likely very exhausted Levallois cores.
Other frequent core types are Core on Flakes and single platform cores; the latter characterize the upper units but are absent from Unit 11. Half of the cores in the assemblage were found in an exhausted stage, maybe due to limited nodule size and not lack of raw material near the site.
This can maybe also be seen in core metric attributes. Maximum length of cores in Nahal Aqev range between 128-25 mm (average 61.6 mm) and are larger than average in Unit 11.  Blanks modified by retouch constitute 2.9% of the flaked items >2 cm (0.78% of the total assemblage) and are dominated by retouched items and notched and denticulated items (S4 Table 2; Fig. S4.6). Levallois blanks were frequently chosen for modification ( Fig. S4.7), and even more prominently in Unit 11. The tool assemblage of Unit 7 is larger and more varied, including a group of small and finely retouched awls and raclettes.    In summary, lithic assemblages from all units excavated in Nahal Aqev share some general attributes, but also differ from one another in some technological aspects. The main differences are between the assemblage from the lower most layer Unit 11 and the rest of the units. Unit 11 is less varied technologically and typologically, and the dominance of the Levallois centripetal flaking method is more prominent in this unit.

Section 5. Luminescence dating
Ten samples were collected in 2016 from the exposed sections, from the archaeological units and from above and below them (S5 Table3) Sampling was carried out under an opaque tarpaulin to prevent any exposure to sunlight, and samples were placed immediately into light-tight black bags .
The source of the quartz in the sediment is aeolian, and all surrounding bedrock is limestone.
The quartz was blown in during dust storms and is deposited on the surface, and later washed into the streams and deposited in the terraces. On average modern dust contains ~30% quartz in the very-fine-sand to fine-silt size fractions, and in the past dust had a similar grain size distribution and composition (31)(32).
Quartz in the size range of 90-125 µm was extracted and purified using routine laboratory procedures (10). Briefly, after wet sieving to the desired grain size, carbonates were dissolved with 8% hydrochloric acid (HCl). The rinsed and dried sample was passed through a Frantz magnetic separator (33) to remove any undissolved dolomite, heavy minerals, and some feldspars. Three grams of the non-magnetic fraction were etched for 40 minutes in hydrofluoric acid (40%) to dissolve the remaining feldspars and etch the exterior of the quartz grains, followed by soaking overnight in 16% HCl to remove any fluorides that may have precipitated.
This was followed by rinsing and drying.
For seven samples, alkali feldspar (KF) grains were extracted from ~5 gr of the non-magnetic fraction (un-etched) using a one-step density separation with sodium polytungstate with a density of 2.58 gr/cm 3 , followed by light etching with 10% HF for 10 min (34), which removed ~10 µm of the grains' surfaces. in standard single grain discs with an array of 10x10 holes, each with a diameter and depth of 300 µm. The latter are effectively micro-aliquots, as hole diameter is 300 µm whereas grain size was 90-125 µm, such that in each grain hole there were 3-4 grains (37). Twenty-five multi-grain aliquots and 400-500 grain holes were measured for each sample. Micro-aliquot data were screened for further data processing using criteria defined in Porat et al. (38).
To obtain the best measurement conditions, a dose recovery test was carried out for sample NAQ-16. Twelve aliquots were bleached for two hours under natural sunlight and then bleached again in the reader for 100 s using blue diodes, followed by administering a laboratory dose of 78 Gy. This dose was treated as an unknown and measured using the SAR protocol (S5 Table4) under a range of preheat and cutheat conditions. A recovery of 0.95 (the ratio between measured and given dose) was obtained using a preheat temperature of 260°C, a test dose of 8 Gy and a cutheat temperature of 200°C (Fig. S51). These conditions were further used for all quartz measurements .   For all samples, the natural OSL and pIR-IR250 signals are bright and decay fast (Fig. S5.3 a-c), recycling ratios on dose response curves are close to unity and recuperation is negligible (   The average ratio between the quartz SG ages and the corresponding multigrain ages is 1, but if we disregard sample NAQ-7 (at 3.6 m), whose SG age is ~40% older than the multi-grain age, then the SG ages are on average ~5% younger than the multigrain ages (S5 Table 3; Fig. S5.

2).
This can be explained by the criteria used for selecting valid SG De values, whereby grains with a high natural signal that cannot be regenerated by the laboratory beta dose are discarded; in multigrain measurements these contribute to the natural signal and De.
The uncorrected KF ages are older than the multi-grain quartz ages by 8-21 ka, and the difference increases with depth. This difference probably indicates that for the older samples, However, corrections increase the KF ages by 8 to 17 ka, depending on the specific fading rate and uncorrected age; they also increase the errors on the ages, particularly for samples with large errors on the fading rates. Nonetheless, in the case of Nahal Aqev, the corrected KF ages agree better with the age obtained from micro-tephra analyses (see below).  Overall, the ages increase with depth up to ~ 2.3 m, and below that are almost constant (Fig.   S5.2). As the De values of the KF continue to increase with depth ( Fig. S5.4), we have no reason to suspect that the pIR-IR250 ages are in saturation; rather the case here is of rapid sedimentation.
The ages increase with depth up to ~ 2 m, and below that are almost constant. One outlier is the paired samples NAQ-4 and NAQ-6, both from the same layer at 2.3 m depth but from different aspects of the excavation walls. It is not possible to assess which sample better represents the age of that unit, as (the younger) NAQ-6 is in agreement with the overlying sample NAQ-3, while (the older) NAQ-4 is within the range of the underlying sample NAQ-5. It is worth noting that the De values of those samples are similar for both quartz and KF (Fig. S4), suggesting that the dose rates of either samples might have not been estimated correctly.
With these considerations in mind and using the fading corrected pIR-IR250 KF ages, our best estimates for the ages of archaeological Units 7, 9 and 11 are as follows: Sample NAQ-5 gives an age of 131±23 ka for Unit 7; sample NAQ-7 gives an age of 132±7 ka for Unit 9; and samples NAQ-8 and NAQ-9 bracket Unit 11 to between 117±7 ka and 134±7 ka. Overall, the ages all fall within the very end of marine isotopic stage (MIS) 6 and early MIS 5. The ages for Unit 11 agree very well with the age obtained from the micro-tephra analyses of 126-128 ka from the same Unit (See Fig. 4 in main text).

Cryptotephra sampling
Samples for cryptotephra analysis were collected at Nahal Aqev in September 2019 at 5 cm consecutive and contiguous intervals from existing and freshly cleaned profiles of the site (

Cryptotephra processing
In the laboratory, individual sediment sub-samples weighing ~2-3 g were extracted from the 41 bulk sediment samples, with three to four of these combined to form composite or 'scan' samples. 13 scan samples were produced to span the sampled Nahal Aqev sequence.
Scan samples were placed in an oven overnight at 105°C to establish their dry weight and combusted in a laboratory muffle furnace for two hours at 550°C to remove organic detritus.
Residual material was immersed in 10% Hydrochloric acid (HCL) to dissolve carbonates before being passed through nylon sieve meshes with apertures of 125 and 15 μm. All material in this size fraction was retained for further processing.
The extraction of volcanic glass shards was conducted using a stepped density separation procedure and the inert heavy liquid sodium polytungstate (SPT) (Na6 (H2W12O40) H2O) (see Blockley et al., 2005). An initial 'cleaning' phase was conducted using the SPT at a specific gravity of 2.00 g/cm 3 , and an 'extraction' phase using SPT with a specific gravity of 2.55 g/cm 3 (51).
Material from the extraction phase was pipetted onto glass microscope slides and mounted under a coverslip using Canada balsam.

Cryptotephra identification & quantification
Microscope slides were examined using an Olympus CX-41 transmitted light microscope. Slides were traversed systematically, and counts were conducted at 20x magnification, an objective with 40x magnification was used to examine morphological detail and to assist in distinguishing volcanic glass shards from non-glass detrital 'mimics'.
No tephra was found in Column 1 or 2A, however, glass shard abundance was exceptionally high in Column 2 and in particular the scan sample T19-0206 (S6 Table 5). In order to ascertain the precise interval of greatest glass shard concentration, the four 5 cm sediment samples that comprise T19-0206 were re-sampled and processed following the methodology outlined above.
To facilitate easier assay of glass shard concentrations the processed samples were spiked with Lycopodium spores prior to mounting onto glass slides (52). Quantification of glass shard concentrations used the following: where c = concentration of glass shards, = total Lycopodium, a = glass shard count, b = Lycopodium count, d = sample dry weight in grams.
Concentrations of glass shards were high in the four samples, however, a distinct peak in concentration was identified at a depth of 75-70 cm (S6 Table 5).

Cryptotephra chemical characterization
The 75-70 cm interval was prepared for major element chemical characterisation using the method outlined above, but with the notable omission of the combustion stage to avoid thermal alteration of the glass shards. Following density separation, residual material was kept in deionised water and pipetted onto glass well-slides. Individual glass shards were extracted using a 5 μl gas chromatography syringe fitted with a 100 μm-diameter needle. These were transferred to a flat silicon sheet and impregnated in an epoxy resin to form a 'stub'. Once hardened, the resin at the surface of the stub was removed using a series of graded silicon papers until the glass shards were exposed and sectioned. A final polish using 0.3 μm aluminium oxide powder provided a flat surface for analysis (53). The resin stub was carbon coated and analysed for major and minor elements at the WDS-EPMA (Cameca SX-100) facility at the University of Edinburgh. Probe conditions followed those of Hayward (54). Samples were analysed using a beam diameter of 8 μm set at 15 keV, and a current of 0.5 nA for Na and Al, 2 nA for Si, K, Ca, Fe and 80 nA for Mg, P, Ti, Mn. 26 successful (SiO2 wt. % > 93%) analyses were obtained.
Calibration, precision and drift was assessed by the analysis of internal Lipari and BCR-2G secondary standards.

Cryptotephra results & interpretation
The occurrence of cryptotephra within the Nahal Aqev site is exclusive to Column 2 where it forms a distinct peak within the base of Unit 11. Refinement of the 'scan' of cryptotephra investigation phase shows a discrete peak in glass shard concentrations in the 75-70 cm interval (S6 Table 5). Cryptotephra concentrations are of a magnitude less in the underlying interval and reduce gradually in the overlying intervals. This pattern of distribution indicates a point of primary tephra deposition within the 75-70 cm interval which can be interpreted as the result of airfall from a passing volcanic ash cloud (c.f. 55). Major and minor element chemical characterisation of the volcanic glass shards (S6 Table 6) reveals a homogenous calc-alkaline rhyolitic composition (Fig. S6.1). Chemical comparison to neighboring volcanic centres and sedimentary archives containing cryptotephras suggests the correlation to a widespread early MIS 5e tephra found in Eastern Mediterranean marine cores (see main text). Within the broad timeframe provided by the OSL dating there is a clear chemical correlation to tephra from early in the Saporpel S5 deposits of cores LC-21 and ODP-967. As shown in figure S6.2 and also summary plots in the main text this is a tight chemical match. Moreover, the chemistry of these tephra is relatively rare in the Eastern Mediterranean and is the only reported primary airfall of these highly evolved, low CaO and FeO tephra for tens of thousands of years.